Repeated results when running a cursor in MySQL

I have a function in MySQL that has a cursor. For the comparisons in sybase you must return two results, but it returns 3 since the second one that returns repeats it. How can I solve it?

I leave the code of the function:

delimiter //
create function dba.fn_atl_sap_fac_imp(vCOD_CLI_FAC decimal(30,6), vID_FAC bigint(30)) returns text
begin
DECLARE ID_IVA CHAR(2);
DECLARE vIMP_IVA CHAR(15);
DECLARE BASE_IVA CHAR(15);
DECLARE IMPORTE_FACTURADO DEC(20, 6);
DECLARE importe_facturado_iva DEC(20, 6);
DECLARE DIFERENCIA DEC(20, 6);
DECLARE numero int;
DECLARE return_Impuesto long VARCHAR;
declare FIN int;


DECLARE csr_IVA_FAC_PAR CURSOR FOR 
        SELECT 
        concat(replace(space(2-length(iva.ID_IVA_SAP)), ' ', '0') , iva.ID_IVA_SAP),
        concat(replace(space(15-length(convert(i.IMP_IVA*100,signed))), ' ', '0'),convert(i.IMP_IVA*100,signed)),
        concat(replace(space(15-length(convert(i.BASE_IVA*100,signed))), ' ', '0'),convert(i.BASE_IVA*100,signed))
        FROM IVA_FAC_PAR i
            join IVA on (iva.id_iva = i.id_iva)
        WHERE #IVA_FAC_PAR.COD_CLI_FAC=vCOD_CLI_FAC AND 
            i.ID_FAC=vID_FAC;

DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET FIN = 1;

set return_Impuesto='';
set numero=0;

SELECT 
    IMP_FAC
INTO IMPORTE_FACTURADO FROM
    FAC_PAR
WHERE
    FAC_PAR.ID_FAC = vID_FAC;


SELECT 
    SUM(i.IMP_IVA + i.BASE_IVA)
INTO importe_facturado_iva FROM
    IVA_FAC_PAR i
WHERE
    i.ID_FAC = vID_FAC;


SET DIFERENCIA = IMPORTE_FACTURADO - importe_facturado_iva;


OPEN csr_IVA_FAC_PAR;

CICLO:loop
        IF FIN THEN
            LEAVE CICLO;
        END IF;
FETCH csr_IVA_FAC_PAR into ID_IVA, vIMP_IVA, BASE_IVA;

IF DIFERENCIA <> 0 THEN
    SET vIMP_IVA = vIMP_IVA/100;
    SET vIMP_IVA = vIMP_IVA + DIFERENCIA;
    SET vIMP_IVA=concat(replace(space(15-length(convert(vIMP_IVA*100,signed))), ' ', '0'),convert(vIMP_IVA*100,signed));
    SET DIFERENCIA = 0;
END IF;

SET numero= numero + 1;

SET return_Impuesto = concat(return_Impuesto,'T ', ID_IVA , vIMP_IVA , BASE_IVA , ';');  


end loop CICLO;
CLOSE csr_IVA_FAC_PAR;

return return_Impuesto;
end;